* {
    padding: 0px;
    margin: 0px;
}

html,
body,
#app {
    width: 100%;
    height: 100%;
}

.main {
    min-width: 320px;
    max-width: 640px;
    margin: 0 auto;
}

.fl {
    float: left;
}

.fr {
    float: right;
}

.clearfix::after {
    content: "";
    clear: both;
    display: block;
}